FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in          Games  Calendar Log in to check your private messages    A possible problem with Simple Sudoku          Sudoku Programmers Forum Index -> Solving sudoku View previous topic :: View next topic   Author Message datafarmer Joined: 05 Feb 2007 Posts: 2 : Items Posted: Mon Feb 05, 2007 2:09 am    Post subject: A possible problem with Simple Sudoku I came across a hint in Simple Sudoku that I cannot understand. link to picture of problem: well I gotta give the board credit on its restriction on web links by new members I cannot figure a way around it besides posting 4 gratituious garbage posts somewhere. One last try ... http://i15.tinypic.com/2dvuan5.png replace the dots, its the best I could come up with. the hint is "exclude based on multiple colors," but I cannot see how that eliminates the highlighted cell. I can see that blue must be false because it shows up in groups with both pink and amber but I am not seeing the hinted at one. that 4 can certainly be eliminated but I eliminate it by making the green square a 4. What am I missing here? Back to top daj95376 Joined: 05 Feb 2006 Posts: 349 : Items Posted: Mon Feb 05, 2007 4:06 am    Post subject: Welcome to the forum. There are several ways to interpret eliminations on <4> in your puzzle. Code: *-----------------------------* | .  4  4 | .  4  . | 4  .  4 | | .  4  4 | .  4  . | 4  .  . | |G4  .  . | .  .  . | .  . B4 | |---------+---------+---------| | .  .  . | .  .  . | .  .  . | | .  .  . | .  .  . | .  .  . | | .  4  4 | .  .  . | .  .  . | |---------+---------+---------| | . A4  . | .  .  . | .  . P4 | | .  .  . | .  .  . | .  .  . | |B4  .  4 | .  .  . | 4  .  4 | *-----------------------------* First, SS always pairs Blue-Green and Pink-Amber for Multi-Colors. At this point in your puzzle, Blue and Pink are in the same unit [r9]. According to the rule for Multi-Colors eliminations, any cell that sees both a Green cell and an Amber cell can have the common digit, <4>, eliminated. As it turns out, [r1c2] is the first cell where an elimination can occur as you scan the grid from upper-left to lower-right. So, [r1c2] is flagged by SS. However, it's also easy to see that [r2c2] and [r9c1] also qualify. Now, as you've pointed out, Blue sees both Pink and Amber. Since at least one Pink or Amber cell must be true, this means that at least one of the Blue cells must be false. But, when one Blue is false, then they are all false. So, you could simply choose to eliminate <4> in all the Blue cells. However, in this situation, I simply bypass thinking in terms of eliminations and flip the logic to assignments. In particular, I would set all Green cells true at this point. In your grid, I would set [r3c1]=4. This isn't in any of the rules, but it makes playing by hand go easier. Finally, if you only look at [r3] and [r7], then you have a Skyscraper -- which may be difficult to understand until you realize that it's lying on its side. Anyway, this is the most trivial form of Multi-Colors and has its own identification because of it. Have I completely confused you? If so, then I'm sorry! Last edited by daj95376 on Mon Feb 05, 2007 6:23 am; edited 2 times in total Back to top angusj Site Admin Joined: 18 Jun 2005 Posts: 406 : Items Posted: Mon Feb 05, 2007 4:08 am    Post subject: Re: A possible problem with Simple Sudoku datafarmer wrote: I can see that blue must be false because it shows up in groups with both pink and amber That's correct. Quote: but I am not seeing the hinted at one ... What am I missing here? We won't know without the original starting position. Paste the starting position here as text (after copying it to the clipboard from Simple Sudoku - Ctrl+C) so it'll be easy for us to copy back into the program. Back to top datafarmer Joined: 05 Feb 2007 Posts: 2 : Items Posted: Mon Feb 05, 2007 4:23 am    Post subject: Ah, that did it, I was missing the obvious after all. For whatever reason when I am doing colors I seem to forget to use squares as a group, I understand the concept but I simply don't see them sometimes. Thanks for the quick reply. On preview I see Angus himself has replied. The problem was really my stupidity. It seems to me that in other cases where more than one could be eliminated the hint would highlight them all and this time it didn't but that could be my faulty memory or my faulty logic. In case it helps here is the initial puzzle: Code:  *-----------*  |...|2..|.9.|  |9..|3.5|..2|  |.26|.1.|3..|  |---+---+---|  |.9.|...|..1|  |3..|829|..6|  |6..|...|.5.|  |---+---+---|  |..8|.6.|91.|  |1..|4.3|..7|  |.5.|..2|...|  *-----------* Supurb program by the way. Thanks for wasting many many hours of my life Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         Sudoku Programmers Forum Index -> Solving sudoku All times are GMT Page 1 of 1   Jump to: Select a forum Sudoku----------------Solving sudokuSetting sudokuProgramming sudokuThe mathematics of sudokuExotic sudoku Library----------------PuzzlesSoftwareSudoku elsewhere Not sudoku----------------Random thoughtsForum feedback  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum   Powered by phpBB © 2001, 2005 phpBB Group Igloo Theme Version 1.0 :: Created By: Andrew Charron